Department of Anatomy and Clinical Anatomy, School of Medicine, University of Zagreb Zagreb, Croatia.
Department of Neuroscience, Croatian Institute for Brain Research, School of Medicine, University of Zagreb Zagreb, Croatia.
Front Neuroanat. 2014 Jun 26;8:50. doi: 10.3389/fnana.2014.00050. eCollection 2014.
The vast majority of cortical GABAergic neurons can be defined by parvalbumin, somatostatin or calretinin expression. In most mammalians, parvalbumin and somatostatin interneurons have constant proportions, each representing 5-7% of the total neuron number. In contrast, there is a threefold increase in the proportion of calretinin interneurons, which do not exceed 4% in rodents and reach 12% in higher order areas of primate cerebral cortex. In rodents, almost all parvalbumin and somatostatin interneurons originate from the medial part of the subpallial proliferative structure, the ganglionic eminence (GE), while almost all calretinin interneurons originate from its caudal part. The spatial pattern of cortical GABAergic neurons origin from the GE is preserved in the monkey and human brain. However, it could be expected that the evolution is changing developmental rules to enable considerable expansion of calretinin interneuron population. During the early fetal period in primates, cortical GABAergic neurons are almost entirely generated in the subpallium, as in rodents. Already at that time, the primate caudal ganglionic eminence (CGE) shows a relative increase in size and production of calretinin interneurons. During the second trimester of gestation, that is the main neurogenetic stage in primates without clear correlates found in rodents, the pallial production of cortical GABAergic neurons together with the extended persistence of the GE is observed. We propose that the CGE could be the main source of calretinin interneurons for the posterior and lateral cortical regions, but not for the frontal cortex. The associative granular frontal cortex represents around one third of the cortical surface and contains almost half of cortical calretinin interneurons. The majority of calretinin interneurons destined for the frontal cortex could be generated in the pallium, especially in the newly evolved outer subventricular zone that becomes the main pool of cortical progenitors.
绝大多数皮质 GABA 能神经元可通过 parvalbumin、somatostatin 或 calretinin 的表达来定义。在大多数哺乳动物中，parvalbumin 和 somatostatin 中间神经元的比例是恒定的，分别占总神经元数的 5-7%。相比之下，calretinin 中间神经元的比例增加了三倍，在啮齿动物中不超过 4%，而在灵长类大脑皮质的高级区域则达到 12%。在啮齿动物中，几乎所有的 parvalbumin 和 somatostatin 中间神经元都来源于侧脑室下区（subpallial）增殖结构的内侧部分，即神经节隆起（ganglionic eminence，GE），而几乎所有的 calretinin 中间神经元都来源于其尾部。GE 起源的皮质 GABA 能神经元的空间模式在猴子和人类大脑中是保守的。然而，可以预期的是，进化正在改变发育规则，以实现 calretinin 中间神经元群体的显著扩张。在灵长类动物的早期胎儿期，皮质 GABA 能神经元几乎完全在侧脑室下区产生，就像在啮齿动物中一样。此时，灵长类动物的尾部神经节隆起（CGE）已经显示出相对增大和 calretinin 中间神经元的产生增加。在妊娠中期，即灵长类动物的主要神经发生阶段，没有在啮齿动物中发现明确的对应物，观察到皮质 GABA 能神经元的顶叶产生以及 GE 的持续扩展。我们提出，CGE 可能是后部和外侧皮质区域 calretinin 中间神经元的主要来源，但不是额叶皮质的主要来源。联合颗粒状额叶皮质代表了大约三分之一的皮质表面，包含了几乎一半的皮质 calretinin 中间神经元。额叶皮质的大部分 calretinin 中间神经元可能是在顶叶中产生的，尤其是在新进化的外 subventricular 区，它成为皮质祖细胞的主要来源。
